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Routing data base for mail

/uussrr/lliibb/mmaaiill/ppaatthhss

File /uussrr/lliibb/mmaaiill/ppaatthhss holds the data base used by the COHERENT
mail system  to route mail.  Each  line gives routing information
to a host, and has the following format:


        host    route   [cost]


_h_o_s_t  names a  UUCP  host.  Because  ssmmaaiill  uses a  binary-search
algorithm when searching the data base for a given host name, the
lines in  ppaatthhss must  be sorted  into ascending order.   (See the
Lexicon entry for  bbsseeaarrcchh for details on binary searches.) ssmmaaiill
ignores case  when it searches ppaatthhss, so  you should convert each
host name to lower case before you sort ppaatthhss.

The _r_o_u_t_e  field details the route by which  mail can travel from
your system to _h_o_s_t.  Note that it includes a pprriinnttff-style format
string.

The optional  field _c_o_s_t is  used by the COHERENT  mail system to
decide whether  to queue outbound UUCP mail,  or to invoke uuuucciiccoo
to  deliver the  mail immediately.   If the _c_o_s_t  is at  or below
ssmmaaiill's  ``queueing  threshold'',  then  ssmmaaiill  will  attempt  to
deliver it immediately.   This speeds mail delivery between hosts
that enjoy  an inexpensive UUCP link, such  as a hard-wired line,
and batches mail that must  be sent over expensive media, such as
long-distance  telephone.  If  the  _c_o_s_t field  is absent,  ssmmaaiill
gives  this  host  a  cost  value  above  that  of  its  queueing
threshold.

***** Example *****

The following  gives a  sample ppaatthhss  file for a  COHERENT system
that its owner has named lleeppaannttoo.


friend  friend!%s       300
hubsys  hubsys!%s       95
lepanto %s      0
lepanto.ampr.org        %s      0
smart-host      hubsys!%s       95
widget  hubsys!widget!%s        95


As  this file  shows,  lleeppaannttoo is  linked to  systems hhuubbssyyss  and
ffrriieenndd.  The cost  of 95  associated with hhuubbssyyss  is low,  and is
appropriate to a low-cost link, such as a hard-wired link; On the
other hand, the cost of 300 associated with ffrriieenndd is high, which
indicates that the connection with ffrriieenndd is high-cost, such as a
long-distance telephone  connection.  If cost is  100 or greater,


COHERENT Lexicon                                           Page 1




paths                 Technical Information                 paths



mail will be queued for latter delivery.  A cost below 100 causes
ssmmaaiill to attempt immediate delivery.

In this  example, machine lleeppaannttoo  is registered in  the aammpprr.oorrgg
Amateur  Packet Radio  domain.   Note that  machine name  lleeppaannttoo
appears in  both conventional and  domain forms in  order to help
resolve addressing.

In order to avoid having to  maintain a huge data base, the owner
of  lleeppaannttoo   uses  hhuubbssyyss  as  a   _s_m_a_r_t  _h_o_s_t.  The  ssmmaarrtt-hhoosstt
designation in  the ppaatthhss data base signals  ssmmaaiill to forward any
mail that it doesn't know how to deliver onto site hhuubbssyyss.

Finally, lleeppaannttoo can use hhuubbssyyss  to pass mail on to wwiiddggeett. Thus,
when rrmmaaiill  receives mail for system wwiiddggeett,  it will transmit it
to hhuubbssyyss for  forwarding.  Note that hhuubbssyyss's administrator must
have given lleeppaannttoo permission to use  it as a mail relay, or this
would not work.

***** See Also *****

mmaaiill, tteecchhnniiccaall iinnffoorrmmaattiioonn



































COHERENT Lexicon                                           Page 2

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